Protocols for the preparation of isospecific .alpha.-olefin polymers may require use of only the substantially pure rac isomer of a symmetrical metallocene catalyst. Likewise, only the meso isomer is useful to implement certain non-isospecific .alpha.-olefin polymerization protocols. Typical metallocene catalyst ligand synthesis yields a mixture containing about equal amounts of the meso and rac isomers. Consequently, half of the chemicals used in the ligand synthesis is wasted. Various metallocene .alpha.-olefin isospecific polymerization catalysts which have no meso form have been suggested to solve this problem. See, e.g., European patent EP 544,308 and U.S. Pat. No. 5,612,428.
A need exists for technology practically useful to resolve mixtures of rac and meso metallocene ligands, and to convert substantially pure rac and meso metallocene ligands to the correspondingly substantially pure meso or the correspondingly substantially pure rac isomers.